1. Field of the Invention
The present invention relates to an image data processing apparatus, an image data processing method, and an image data processing program that are can be suitably used in, for example, encoders or decoders. Particularly, the present invention relates to an image data processing apparatus, an image data processing method, and an image data processing program that can reduce the processing required to embed a code into image data or decode the code.
2. Description of the Related Art
U.S. Pat. No. 5,636,292 and Japanese Patent Application Laid-Open No. 2000-299779 disclose embedding of separate data (such as a code) into image data or audio data to prevent falsifications, prevent an illicit use, and provide additional services.
As the technique is applied for a security purpose, conventional methods are designed to be able to bear a deformation of original data or a request for a partial use. For example, a very complex method (such as a digital watermark) is conventionally employed such as a spread disposition of the same data within an image or inputting data in a frequency region using a Fast Fourier Transformation (FFT).
The digital watermark technique is applied to various additional services. For example, U.S. Pat. No. 5,841,978 discloses a method of reading a digital watermark embedded into a printed material, and displaying a specific web page.
In the conventional technique of embedding a digital watermark, it is necessary to calculate the FFT. However, it requires a huge number of calculations to be performed to calculate the FFT.
It is practically difficult to embed or read data into or from the image data in portable information devices (portable telephone, PHS (Personal Handy phone System), PDAs (Personal Digital Assistant) and the like because these devices have limited resources such as less memory capacity or slower processors.
These together with other aspects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.